node current (c : bool; x : int on c) returns ( y : int )
let
  y = merge c (true -> x) (false -> 0 fby y whenot c)
tel

node internal_current (c : bool; x : int on c) returns ( y : int on c)
var x_cur : int;
let
  x_cur = merge c (true -> x) (false -> 0 fby x_cur whenot c);
  y = x_cur when c
tel

node use_current (c : bool; x : int) returns (y : int on c)
var x_cur :int;
let
  x_cur = current(c,x);
  y = x_cur when c;
tel